Only allow one shadowRoot.

sky/engine/core/dom/shadow/ShadowRoot.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 13 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef SKY_ENGINE_CORE_DOM_SHADOW_SHADOWROOT_H_
 #define SKY_ENGINE_CORE_DOM_SHADOW_SHADOWROOT_H_
 
 #include "sky/engine/core/dom/ContainerNode.h"
 #include "sky/engine/core/dom/DocumentFragment.h"
 #include "sky/engine/core/dom/Element.h"
 #include "sky/engine/core/dom/TreeScope.h"
-#include "sky/engine/wtf/DoublyLinkedList.h"
 
 namespace blink {
 
 class Document;
 class ElementShadow;
 class ExceptionState;
 class InsertionPoint;
 class ShadowRootRareData;
 class StyleSheetList;
 
-class ShadowRoot final : public DocumentFragment, public TreeScope, public DoublyLinkedListNode<ShadowRoot> {
+class ShadowRoot final : public DocumentFragment, public TreeScope {
     DEFINE_WRAPPERTYPEINFO();
-    friend class WTF::DoublyLinkedListNode<ShadowRoot>;
 public:
 
     static PassRefPtr<ShadowRoot> create(Document& document)
     {
         return adoptRef(new ShadowRoot(document));
     }
 
     void recalcStyle(StyleRecalcChange);
 
     // Disambiguate between Node and TreeScope hierarchies; TreeScope's implementation is simpler.
     using TreeScope::document;
     using TreeScope::getElementById;
 
     Element* host() const { return toElement(parentOrShadowHostNode()); }
     ElementShadow* owner() const { return host() ? host()->shadow() : 0; }
 
-    ShadowRoot* youngerShadowRoot() const { return prev(); }
-
-    bool isYoungest() const { return !youngerShadowRoot(); }
-    bool isOldest() const { return !olderShadowRoot(); }
-    bool isOldestAuthorShadowRoot() const;
-
     virtual void insertedInto(ContainerNode*) override;
     virtual void removedFrom(ContainerNode*) override;
 
     void registerScopedHTMLStyleChild();
     void unregisterScopedHTMLStyleChild();
 
     bool containsContentElements() const;
     bool containsInsertionPoints() const { return containsContentElements(); }
     bool containsShadowRoots() const;
 
     // For Internals, don't use this.
     unsigned childShadowRootCount() const;
     unsigned numberOfStyles() const { return m_numberOfStyles; }
 
     void didAddInsertionPoint(InsertionPoint*);
     void didRemoveInsertionPoint(InsertionPoint*);
     const Vector<RefPtr<InsertionPoint> >& descendantInsertionPoints();
 
     // Make protected methods from base class public here.
     using TreeScope::setDocument;
     using TreeScope::setParentTreeScope;
 
 public:
     Element* activeElement() const;
 
-    ShadowRoot* olderShadowRoot() const { return next(); }
-
     PassRefPtr<Node> cloneNode(bool, ExceptionState&);
     PassRefPtr<Node> cloneNode(ExceptionState& exceptionState) { return cloneNode(true, exceptionState); }
 
     StyleSheetList* styleSheets();
 
 private:
     ShadowRoot(Document&);
     virtual ~ShadowRoot();
 
 #if !ENABLE(OILPAN)
     virtual void dispose() override;
 #endif
 
     ShadowRootRareData* ensureShadowRootRareData();
 
     void addChildShadowRoot();
     void removeChildShadowRoot();
     void invalidateDescendantInsertionPoints();
 
     // ShadowRoots should never be cloned.
     virtual PassRefPtr<Node> cloneNode(bool) override { return nullptr; }
 
-    // FIXME: This shouldn't happen. https://bugs.webkit.org/show_bug.cgi?id=88834
-    bool isOrphan() const { return !host(); }
-
-    RawPtr<ShadowRoot> m_prev;
-    RawPtr<ShadowRoot> m_next;
     OwnPtr<ShadowRootRareData> m_shadowRootRareData;
     unsigned m_numberOfStyles : 27;
     unsigned m_registeredWithParentShadowRoot : 1;
     unsigned m_descendantInsertionPointsIsValid : 1;
 };
 
 inline Element* ShadowRoot::activeElement() const
 {
     return adjustedFocusedElement();
 }
 
 DEFINE_NODE_TYPE_CASTS(ShadowRoot, isShadowRoot());
 DEFINE_TYPE_CASTS(ShadowRoot, TreeScope, treeScope, treeScope->rootNode().isShadowRoot(), treeScope.rootNode().isShadowRoot());
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_DOM_SHADOW_SHADOWROOT_H_